Concrete leach

A new report claims that the leaching performance of concrete containing recycled aggregates is similar to that of concrete made using primary sources.

New research published by WRAP (Waste & Resources Action Programme) has shown that the leaching performance of concrete containing recycled and secondary aggregates is similar to that of concrete made using aggregates from primary sources.

Using a variety of secondary and recycled aggregates – including recycled asphalt planings, foundry sand, incinerator bottom ash, crushed concrete and crushed brick – the report analysed the potential for elements within the aggregates to be leached from concrete into controlled waters such as groundwater and drinking water.

The study also determined that the best method of evaluating the suitability of recycled and secondary aggregates for use in concrete in relation to their release of undesirable substances was testing the material in accordance with British Standard BS EN 1744-3:2002. This refers to a rapidly stirred tank test carried out on crushed aggregate material and is based on the assumption that equilibrium or near-equilibrium is achieved between the liquid and solid phases during the test period.

‘Recycled and secondary aggregates have a key role to play in making the construction industry more sustainable and it’s important the industry is able to have full confidence in using these materials,’ explained John Barritt, technical advisor for aggregates at WRAP.

‘It’s also important the materials are shown not to have an adverse impact on either the properties of concrete or the environment in which they are used. We were pleased to note the study found the performance of both primary aggregate and aggregates that come from recycled and secondary sources to be very similar. We also identified a reliable testing method that can be used to determine the likely leaching performance of individual aggregates when used in concrete,’ he added.

The full report, “Testing of Concrete to Determine the Effects on Groundwater” can be found at WRAP’s AggRegain website.